/* crypto/dsa/dsa_ossl.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
* This package is an SSL implementation written
* by Eric Young (eay@cryptsoft.com).
* The implementation was written so as to conform with Netscapes SSL.
*
* This library is free for commercial and non-commercial use as long as
* the following conditions are aheared to. The following conditions
* apply to all code found in this distribution, be it the RC4, RSA,
* lhash, DES, etc., code; not just the SSL code. The SSL documentation
* included with this distribution is covered by the same copyright terms
* except that the holder is Tim Hudson (tjh@cryptsoft.com).
*
* Copyright remains Eric Young's, and as such any Copyright notices in
* the code are not to be removed.
* If this package is used in a product, Eric Young should be given attribution
* as the author of the parts of the library used.
* This can be in the form of a textual message at program startup or
* in documentation (online or textual) provided with the package.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.]
*/
/* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
#include <stdio.h>
#include "cryptlib.h"
#include <openssl/bn.h>
#include <openssl/sha.h>
#include <openssl/dsa.h>
#include <openssl/rand.h>
#include <openssl/asn1.h>
static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
BIGNUM **kinvp, BIGNUM **rp,
const unsigned char *dgst, int dlen);
static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
DSA *dsa);
static int dsa_init(DSA *dsa);
static int dsa_finish(DSA *dsa);
static DSA_METHOD openssl_dsa_meth = {
"OpenSSL DSA method",
dsa_do_sign,
dsa_sign_setup,
dsa_do_verify,
NULL, /* dsa_mod_exp, */
NULL, /* dsa_bn_mod_exp, */
dsa_init,
dsa_finish,
0,
NULL,
NULL,
NULL
};
/* These macro wrappers replace attempts to use the dsa_mod_exp() and
* bn_mod_exp() handlers in the DSA_METHOD structure. We avoid the problem of
* having a the macro work as an expression by bundling an "err_instr". So;
*
* if (!dsa->meth->bn_mod_exp(dsa, r,dsa->g,&k,dsa->p,ctx,
* dsa->method_mont_p)) goto err;
*
* can be replaced by;
*
* DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, &k, dsa->p, ctx,
* dsa->method_mont_p);
*/
#define DSA_MOD_EXP(err_instr,dsa,rr,a1,p1,a2,p2,m,ctx,in_mont) \
do { \
int _tmp_res53; \
if((dsa)->meth->dsa_mod_exp) \
_tmp_res53 = (dsa)->meth->dsa_mod_exp((dsa), (rr), (a1), (p1), \
(a2), (p2), (m), (ctx), (in_mont)); \
else \
_tmp_res53 = BN_mod_exp2_mont((rr), (a1), (p1), (a2), (p2), \
(m), (ctx), (in_mont)); \
if(!_tmp_res53) err_instr; \
} while(0)
#define DSA_BN_MOD_EXP(err_instr,dsa,r,a,p,m,ctx,m_ctx) \
do { \
int _tmp_res53; \
if((dsa)->meth->bn_mod_exp) \
_tmp_res53 = (dsa)->meth->bn_mod_exp((dsa), (r), (a), (p), \
(m), (ctx), (m_ctx)); \
else \
_tmp_res53 = BN_mod_exp_mont((r), (a), (p), (m), (ctx), (m_ctx)); \
if(!_tmp_res53) err_instr; \
} while(0)
const DSA_METHOD *DSA_OpenSSL(void)
{
return &openssl_dsa_meth;
}
static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
{
BIGNUM *kinv=NULL,*r=NULL,*s=NULL;
BIGNUM m;
BIGNUM xr;
BN_CTX *ctx=NULL;
int reason=ERR_R_BN_LIB;
DSA_SIG *ret=NULL;
int noredo = 0;
BN_init(&m);
BN_init(&xr);
if (!dsa->p || !dsa->q || !dsa->g)
{
reason=DSA_R_MISSING_PARAMETERS;
goto err;
}
s=BN_new();
if (s == NULL) goto err;
ctx=BN_CTX_new();
if (ctx == NULL) goto err;
redo:
if ((dsa->kinv == NULL) || (dsa->r == NULL))
{
if (!dsa->meth->dsa_sign_setup(dsa,ctx,&kinv,&r,dgst,dlen))
goto err;
}
else
{
kinv=dsa->kinv;
dsa->kinv=NULL;
r=dsa->r;
dsa->r=NULL;
noredo = 1;
}
if (dlen > BN_num_bytes(dsa->q))
/* if the digest length is greater than the size of q use the
* BN_num_bits(dsa->q) leftmost bits of the digest, see
* fips 186-3, 4.2 */
dlen = BN_num_bytes(dsa->q);
if (BN_bin2bn(dgst,dlen,&m) == NULL)
goto err;
/* Compute s = inv(k) (m + xr) mod q */
if (!BN_mod_mul(&xr,dsa->priv_key,r,dsa->q,ctx)) goto err;/* s = xr */
if (!BN_add(s, &xr, &m)) goto err; /* s = m + xr */
if (BN_cmp(s,dsa->q) > 0)
if (!BN_sub(s,s,dsa->q)) goto err;
if (!BN_mod_mul(s,s,kinv,dsa->q,ctx)) goto err;
ret=DSA_SIG_new();
if (ret == NULL) goto err;
/* Redo if r or s is zero as required by FIPS 186-3: this is
* very unlikely.
*/
if (BN_is_zero(r) || BN_is_zero(s))
{
if (noredo)
{
reason = DSA_R_NEED_NEW_SETUP_VALUES;
goto err;
}
goto redo;
}
ret->r = r;
ret->s = s;
err:
if (!ret)
{
DSAerr(DSA_F_DSA_DO_SIGN,reason);
BN_free(r);
BN_free(s);
}
if (ctx != NULL) BN_CTX_free(ctx);
BN_clear_free(&m);
BN_clear_free(&xr);
if (kinv != NULL) /* dsa->kinv is NULL now if we used it */
BN_clear_free(kinv);
return(ret);
}
static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
BIGNUM **kinvp, BIGNUM **rp,
const unsigned char *dgst, int dlen)
{
BN_CTX *ctx;
BIGNUM k,kq,*K,*kinv=NULL,*r=NULL;
int ret=0;
if (!dsa->p || !dsa->q || !dsa->g)
{
DSAerr(DSA_F_DSA_SIGN_SETUP,DSA_R_MISSING_PARAMETERS);
return 0;
}
BN_init(&k);
BN_init(&kq);
if (ctx_in == NULL)
{
if ((ctx=BN_CTX_new()) == NULL) goto err;
}
else
ctx=ctx_in;
if ((r=BN_new()) == NULL) goto err;
/* Get random k */
do
{
#ifndef OPENSSL_NO_SHA512
if (dsa->flags & DSA_FLAG_NONCE_FROM_HASH)
{
/* If DSA_FLAG_NONCE_FROM_HASH is set then we calculate k from
* SHA512(private_key + H(message) + random). This protects the
* private key from a weak PRNG. */
if (!BN_generate_dsa_nonce(&k, dsa->q, dsa->priv_key, dgst,
dlen, ctx))
goto err;
}
else
#endif
if (!BN_rand_range(&k, dsa->q)) goto err;
} while (BN_is_zero(&k));
if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
{
BN_set_flags(&k, BN_FLG_CONSTTIME);
}
if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
{
if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
CRYPTO_LOCK_DSA,
dsa->p, ctx))
goto err;
}
/* Compute r = (g^k mod p) mod q */
if ((dsa->flags & DSA_FLAG_NO_EXP_CONSTTIME) == 0)
{
if (!BN_copy(&kq, &k)) goto err;
/* We do not want timing information to leak the length of k,
* so we compute g^k using an equivalent exponent of fixed length.
*
* (This is a kludge that we need because the BN_mod_exp_mont()
* does not let us specify the desired timing behaviour.) */
if (!BN_add(&kq, &kq, dsa->q)) goto err;
if (BN_num_bits(&kq) <= BN_num_bits(dsa->q))
{
if (!BN_add(&kq, &kq, dsa->q)) goto err;
}
K = &kq;
}
else
{
K = &k;
}
DSA_BN_MOD_EXP(goto err, dsa, r, dsa->g, K, dsa->p, ctx,
dsa->method_mont_p);
if (!BN_mod(r,r,dsa->q,ctx)) goto err;
/* Compute part of 's = inv(k) (m + xr) mod q' */
if ((kinv=BN_mod_inverse(NULL,&k,dsa->q,ctx)) == NULL) goto err;
if (*kinvp != NULL) BN_clear_free(*kinvp);
*kinvp=kinv;
kinv=NULL;
if (*rp != NULL) BN_clear_free(*rp);
*rp=r;
ret=1;
err:
if (!ret)
{
DSAerr(DSA_F_DSA_SIGN_SETUP,ERR_R_BN_LIB);
if (r != NULL)
BN_clear_free(r);
}
if (ctx_in == NULL) BN_CTX_free(ctx);
BN_clear_free(&k);
BN_clear_free(&kq);
return(ret);
}
static int dsa_do_verify(const unsigned char *dgst, int dgst_len, DSA_SIG *sig,
DSA *dsa)
{
BN_CTX *ctx;
BIGNUM u1,u2,t1;
BN_MONT_CTX *mont=NULL;
int ret = -1, i;
if (!dsa->p || !dsa->q || !dsa->g)
{
DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MISSING_PARAMETERS);
return -1;
}
i = BN_num_bits(dsa->q);
/* fips 186-3 allows only different sizes for q */
if (i != 160 && i != 224 && i != 256)
{
DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_BAD_Q_VALUE);
return -1;
}
if (BN_num_bits(dsa->p) > OPENSSL_DSA_MAX_MODULUS_BITS)
{
DSAerr(DSA_F_DSA_DO_VERIFY,DSA_R_MODULUS_TOO_LARGE);
return -1;
}
BN_init(&u1);
BN_init(&u2);
BN_init(&t1);
if ((ctx=BN_CTX_new()) == NULL) goto err;
if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
BN_ucmp(sig->r, dsa->q) >= 0)
{
ret = 0;
goto err;
}
if (BN_is_zero(sig->s) || BN_is_negative(sig->s) ||
BN_ucmp(sig->s, dsa->q) >= 0)
{
ret = 0;
goto err;
}
/* Calculate W = inv(S) mod Q
* save W in u2 */
if ((BN_mod_inverse(&u2,sig->s,dsa->q,ctx)) == NULL) goto err;
/* save M in u1 */
if (dgst_len > (i >> 3))
/* if the digest length is greater than the size of q use the
* BN_num_bits(dsa->q) leftmost bits of the digest, see
* fips 186-3, 4.2 */
dgst_len = (i >> 3);
if (BN_bin2bn(dgst,dgst_len,&u1) == NULL) goto err;
/* u1 = M * w mod q */
if (!BN_mod_mul(&u1,&u1,&u2,dsa->q,ctx)) goto err;
/* u2 = r * w mod q */
if (!BN_mod_mul(&u2,sig->r,&u2,dsa->q,ctx)) goto err;
if (dsa->flags & DSA_FLAG_CACHE_MONT_P)
{
mont = BN_MONT_CTX_set_locked(&dsa->method_mont_p,
CRYPTO_LOCK_DSA, dsa->p, ctx);
if (!mont)
goto err;
}
DSA_MOD_EXP(goto err, dsa, &t1, dsa->g, &u1, dsa->pub_key, &u2, dsa->p, ctx, mont);
/* BN_copy(&u1,&t1); */
/* let u1 = u1 mod q */
if (!BN_mod(&u1,&t1,dsa->q,ctx)) goto err;
/* V is now in u1. If the signature is correct, it will be
* equal to R. */
ret=(BN_ucmp(&u1, sig->r) == 0);
err:
/* XXX: surely this is wrong - if ret is 0, it just didn't verify;
there is no error in BN. Test should be ret == -1 (Ben) */
if (ret != 1) DSAerr(DSA_F_DSA_DO_VERIFY,ERR_R_BN_LIB);
if (ctx != NULL) BN_CTX_free(ctx);
BN_free(&u1);
BN_free(&u2);
BN_free(&t1);
return(ret);
}
static int dsa_init(DSA *dsa)
{
dsa->flags|=DSA_FLAG_CACHE_MONT_P;
return(1);
}
static int dsa_finish(DSA *dsa)
{
if(dsa->method_mont_p)
BN_MONT_CTX_free(dsa->method_mont_p);
return(1);
}